A proposed system for writing encoded image data in packets formatted according to the MPEG system on a storage medium to enable trick reproduction of image data by a simple and efficient method without increasing the capacity of the storage medium is to set up an I picture index of packets in which at least part of the I picture data is stored and, during trick reproduction, to read only the packets on which the I picture index is set (for example,    Patent Document No. 1).    Patent Document No. 1: Japanese Patent Application    Publication No. H9-98430 (pp. 4-10, FIGS. 1-15)